Process for the production of chlorine, sodium bicarbonate and ammonium-sodium nitrate

ABSTRACT

A combined process for producing chlorine, sodium bicarbonate and ammonium-sodium nitrate comprising oxidizing sodium chloride with nitric acid solution to form with unreacted nitric acid, sodium nitrate solution and gaseous reaction products including chloride, nitrogen oxide and nitrosyl chloride; oxidizing chlorine compound in said gaseous mixture to chlorine and removing chlorine by liquefaction and distillation or by absorption with solvent; absorbing nitrogen oxides in said gaseous reaction products into nitric acid, neutralizing the solution mixture of sodium nitrate and nitric acid by ammoniation and carbonizing the neutralized product to precipitate sodium carbonate and leave a solution of ammonium-sodium nitrate.

United States Patent [1 1 Pischinger et al.

[54] PROCESS FOR THE PRODUCTION OF CHLORINE, SODIUM BICARBONATE ANDAMMONIUM-SODIUM NITRATE [76] Inventors: Ernest Pischinger, Konopnickiej21a, Torun; Stanislaw Bursa, Malczwskiego 19/5, Szczecin; HenrykKoneczny, Krasinskiego 57/9, Torun; Jerzy Straszko, Ksieciz, Witoldala/10, Szczecin, all of P0- land 22 Filed: Oct. 22, 1971 [21] Appl. No.:191,822

Related US. Application Data [63] Continuation-in-part of Ser. No.808,062, March 18,

[111 3,734,709 May 22,1973

Primary ExaminerSamih N. Zaharna Assistant ExaminerRichard BarnesAttorneylrvin A. Lavine [57] ABSTRACT A combined process for producingchlorine, sodium bicarbonate and ammonium-sodium nitrate comprisingoxidizing sodium chloride with nitric acid solution to form withunreacted nitric acid, sodium nitrate solution and gaseous reactionproducts including chloride, nitrogen oxide and nitrosyl chloride;oxidizing chlorine compound in said gaseous mixture to 1969, abandoned.chlorine and removing chlorine by liquefaction and distillation or byabsorption with solvent; absorbing [52] US. Cl. ..71/59, 423/241,423/399, nitrogen oxides in said gaseous reaction products into 423/423,423/424 nitric acid, neutralizing the solution mixture of sodium [51]Int. Cl ..C05c 13/00 nitrate and nitric acid by ammoniation andcarboniz- [5 8] Field of Search ..7l/59; 423/240, 241, ing theneutralized product to precipitate sodium car- 423/399, 472, 504, 423,424 bonate and leave a solution of ammonium-sodium nitrate. [56]References Cited 5 Claims, 1 Drawing Figure UNITED STATES PATENTS3,062,616 11/1962 Chadwick ..23/102 A NuCl Hun, N0,

5 l 1 Cl NH; FT

NH: a

PROCESS FOR THE PRODUCTION OF CHLORINE, SODIUM BICARBONATE ANDAMMONIUM-SODIUM NITRATE This application is a Continuation-In-Part ofSer. No. 808,062, filed Mar. 18, 1969 and now abandoned.

The invention relates to the combined process for the production ofchlorine, sodium bicarbonate and a concentrated fertilizer in the formof mixtures of ammonium and sodium nitrates. The present productionprocess, in which chlorine, sodium bicarbonate andammonium-sodiumnitrate are obtained as final products is unknown in the technical andpatent literature and are not hitherto used in industrial practice.

The known processes for the production of chlorine and sodiumbicarbonate have several imperfections.

The known oxidation processes of alkali metal chlorides e.g. oxidationof sodium chloride with nitric acid (U.S. Pats. No. 3,062,616,3,062,617, 3,062,618) and of potassium chloride (U.S. Pat. No. 3,211,525) as well as oxidation of alkali metal chlorides with nitrogenoxides (Fr. Pat. No. 1,333,769 and W. German Pat. No. 1,068,676) resultin obtaining chlorine and sodium or potassium nitrate. Oxidation ofsodium chloride results in sodium nitrate, containing the sodium ion andis useless for plants.

Other processes for the production of chlorine e.g. by electrolysis ofpotassium or sodium chlorides yield also hydroxides of these metalswhich are by-products of limited demand.

In the known Solvay process for the production of sodium bicarbonate andsodium carbonate by carbonation of ammoniated sodium chloride solutionburdensome wastes, mainly in the form of calcium chloride are obtained.

In this Solvay process the chloride ion is not thoroughly utilized andit should be additionally bonded by means of calcium from ammoniumchloride in the ammonia regeneration process and removed to waste ponds.

In all these processes mentioned above burdensome wastes andunprofitable by-products are obtained in addition to the final productsor the raw materials are not fully utilized.

The process according to the invention is devoid of disadvantagesmentioned above. In the present process the solution of sodium nitrateand nitric acid is neutralized, saturated with ammonia and carbonatedwith carbon dioxide.

By this reaction sodium bicarbonate precipitates from the solution andmay be further processed into sodium carbonate in known manner. Ammoniumnitrate and unreacted sodium nitrate contained in the solution may beisolated by evaporation, crystallization, centrifuging and drying theobtained nitrate (crystals).

The operations of neutralization and ammoniation of the solution ofsodium nitrate and nitric acid as well as further carbonation of theresulting solution with carbon dioxide are carried out to such a stageas to obtain ammonium-sodium nitrate, containing not less than 70percent by weight of ammonium nitrate and above 30 percent of the totalcontent of nitrogen in a reaction vessel.

In the oxidation of sodium chloride, nitric acid is employed in excess.The nitric acid is preferably at about 60 percent to about 70 percentconcentration for reaction with sodium chloride, while leaving an excessto be ultimately neutralized to provide a sodium-ammonium nitratesolution which is at least about percent by weight ammonium nitrate. Asmall amount of percent nitric acid is preferably present to oxidizenitrosyl chloride to chlorine. Large excesses of nitric acid are notemployed.

The post-reaction solution of oxidation of sodium chloride with anexcess of concentrated nitric acid is passed into a sieve plate column.The post-reaction gaseous mixture contains gaseous reaction productsincluding nitrogen oxides, nitrosyl chloride and chlorine. The gaseousmixture is partially recycled into the reaction vessel into a separateabsorption column wherein nitrosyl chloride is removed from the othergases by oxidation and absorption with a portion of the excess nitricacid and dried by cold treatment. The remaining gas mixture is separatedby means of rectification into nitrogen oxides and chlorine, a finalproduct. The nitrogen oxides are oxidized with cold concentrated nitricacid to form principally nitrogen tetroxide and are then oxidized intoadditional nitric acid by known methods. Chloride ion is substantiallycompletely removed in the foregoing procedure by passing nitrogen oxidesthrough the solution.

The process according to the invention can be combined with theproduction of ammonia which is partly utilized for neutralization andammoniation of the solution of sodium nitrate and nitric acid and partlyfor the production of nitric acid, which is subsequently utilized inoxidation of sodium chloride. 7

Carbon dioxide, formed in the ammonia production, is utilized incarbonation of the ammonia solution containing ammonium and sodiumnitrates.

In the instant invention sodium bicarbonate is formed to leave a mixtureof ammonium and sodium nitrates in solution. Solutions of these nitratescan be concentrated and used as liquid mixed fertilizers, or can beevaporated to obtain the solid mixed nitrate, which can be used as asolid mixed fertilizer.

The outstanding advantages of the combined process for the production ofsodium carbonate chlorine and ammonium-sodium nitrate as compared toother processes previously known and used are as follows: utilization ofall elements contained in raw-materials; great simplification oftechnological system; the possibility of utilization of carbon dioxidewhich has usually been regarded as a waste in the ammonia production.Moreover several operations connected with the utilization or removal ofwastes can be avoided, since there are in practice no wastes in thisprocess.

The initial concentrations of each of the ammonium and sodium nitratescan be controlled by concentrating the mother liquor until it containsabout 30 percent of the total content of nitrogen. In this waycrystallization of only ammonium nitrate is avoided.

In the process of the instant invention chlorine is formed withoutundesirable side production of soda lye which often occurs in theelectrolysis of sodium chloride. Further, sodium bicarbonate (and, ifdesired, sodium carbonate) is formed without distillation residues sincethere is no ammonia regeneration from the stage at which sodiumbicarbonate is formed. Ammonia regeneration is not necessary since inthe initial stages of the reaction nitrate ion replaces chloride ion.Thus, when sodium bicarbonate is formed ammonium nitrate (and notammonium chloride) is also formed. This, in mixture with sodium nitratecan be readily separated from the post-reaction liquor. Consequently,the distillation of ammonia, with the accompanying formation of wastes,which latter is characteristic of the Solvay process, is not required.

In the instant invention the mixture of ammonium and sodium nitrates andan optimal amount of sodium bicarbonate are obtained in quantities whichare conditioned by the respective concentration of the startingmaterials. Further, filtration of the mother liquor is desirablypracticed at about 28 30 C in order to effect separation of sodiumbicarbonate.

Thus ammoniumsodium nitrate mixture is obtained by concentratingsolutions of these nitrates of the respective boiling temperatures ofthese solutions and, if desired, under respective pressures to effectevaporation in a multiple-effect evaporator.

The solution obtained after oxidation of sodium chloride with nitricacid to form a solution including excess nitric acid, sodium nitrate anda gaseous mixture from which chlorine is removed and nitrogen oxides areoxidized to additional nitric acid, which is typically at about 63percent to about 98 percent concentration and which can be used to aidin the oxidation of sodium chloride and of nitrosyl chloride gaseousreaction product typically has the following weight concentrations priorto formation of sodium bicarbonate.

Sodium Nitrate 68.0 parts Ammonium Bicarbonate 49.6 parts Water 100.0parts Ammonium Nitrate 16.0 parts These amounts will make the optimalefficiency of sodium bicarbonate, which is separated as large, wellshaped crystals, and thus a respective ratio of ammonium nitrate tosodium nitrate in solution.

The amounts indicated above influence the amount of nitric acids to beused in excess of the amount required to oxidize sodium chloride whileproviding substantially total oxidation of the chloride ion.

The process according to the invention for the production of sodiumcarbonate, chlorine and ammoniumsodium nitrate is illustrated in theFIGURE in which the particular operation stages of the process aremarked.

The first stage of this combined process in the production of ammonia byone of several known methods, e.g. by the conversion of methane l.Ammonia is being used as a starting material for producing nitric acidby oxidation 2 and also for neutralization 7 and ammoniation of thepost-reaction solution. Carbon dioxide obtained in the ammoniaproduction stage is subsequently utilized to the carbonization stage 8.The solid sodium chloride, obtained after purification 3 is directed tothe oxidation stage 4 with nitric acid.

The gas mixture which is to be rectified in stages, and results from theoxidation stage, contains mainly chlorine, nitrogen oxides and nitrosylchloride. Chlorine compounds are removed from this gas mixture byoxidation in order to obtain gaseous chlorine and its absorption bymeans of excess nitric acid, after stage 5.

The vapors of acids and water are removed from these gases by coldtreatment. The liquid products of sodium chloride oxidation containmainly sodium nitrate, unreacted nitric acid and some amounts ofchlorides, the last being removed by passing nitrogen oxides throughthis solution.

Gaseous reaction products evolving from oxidation of chloride ion andnitrosyl chloride, containing chlorine and nitrogen oxides are directedto rectification stage 5, wherefrom chlorine is withdrawn and collectedas the final product, while nitrogen oxides are absorbed 6 intoadditional nitric acid. The nitric acid typically is of about 63 percentto about 98 percent concentration and assists in the oxidation of sodiumchloride and nitrosyl chloride.

The post-reaction solution, including sodium nitrate and the excess ofnitric acid is neutralized and ammoniated, stage 7. The obtainedammoniated solution of sodium and ammonium nitrates is carbonized, stage8, by means of carbon dioxide obtained from the ammonia synthesis stage1 and calcination stage 10. Sodium bicarbonate, formed in thecarbonization stage 8 is separated from the solution by filtration 9 andcalcinated 10 to sodium carbonate. Either sodium bicarbonate or sodiumcarbonate is collected as a final product and carbon dioxide is directedto decarbonization 11 where residual amounts of carbon dioxide andammonia evolve.

The evolved gases are directed to the neutralization and absorption 7,while the decarbonized solution is concentrated l2 and crystallized l3yielding the final product in form of ammonium-sodium nitrate.

EXAMPLE All parts and percentages are indicated by weight.

A tank reactor at a temperature of 106 C was filled with 495 parts ofevaporated salt containing 467 parts of NaCl and 28.5 parts H O. Nitricacid in'an amount of 1,270 parts of 60 percent nitric acid and 11.5parts of 98 percent nitric acid was introduced into a column. The acidfrom the column at a temperature of C passed to the reactor, in whichNaCl was oxidized. The amounts of HNO and NaCl employed corresponded toa mol ratio of NaCl/HNO of about 2:24zl.

The solution from the reactor, wherein the NaCl is not completelyoxidized, was directed toward a sieve plate column at about 1 10 C. N0was then introduced into this column to take off 283 parts of chlorine,which included chlorine oxidized from nitrosyl chloride with the 63percent to 98 percent nitric acid. Remaining gaseous reaction productsare oxidized to nitric acid and the after-reaction solution amounted to1,765 parts containing 680 parts NaNO 1,000 parts H 0 and 126 partsl-lNO The mol ratio HNO lmol HNO "M03 in the reaction mixture was 0.2:1.

This mixture was neutralized by means of gaseous ammonia (condensedammonia may also by used) in an amount of ammonia in order to obtain amol ratio of NH lNaNO equal to 1:1.

The ammoniated brine which was obtained at a temperature of 40 C has thefollowing composition:

NaNO, 680 parts NH.NO, 160 parts Nl-l 136 parts H,O 1,000 parts Thissolution was carbonated at a temperature of 30 C, to obtain a solutionwith suspended NaHCO The output of the carbonizing process in thecarbonating column was 67 percent theoretical, amounting to 450 parts ofNaHCO The solution was suspended NaHCO, which was at a temperature of 30C was directed towards a rotary fil-- ter. The NaHCO was precipitated bybeing washed out with 130 parts of H 0. The NaHCO which precipitated andwhich could be calcined contained:

450 parts Nal-lCO 1.4 parts NaNO N 0. The soda obtained subsequent tocalcination had the following composition:

73 parts Na,CO, 280 parts NaNO 1.4 parts H,0 I 1.4 parts The filtrateliquor which was at a temperature of 30 C and contained:

NaNO, 233 parts Nl-LNO 583 parts NHJ-ICO; ll0 parts (NH ,CO, 42 partsH,0 931 parts was decarbonized in order to decompose theammoniacarbonate salts and partially evaporate the water, thereby toobtain an equeous solution of NaNO and NILNO mixture at a temperature of85 C which contained:

NaNO; 233 parts Nl-LNO; 583 parts n,o 8.5 parts including chlorine,nitrogen oxides and nitrosyl chloride; oxidizing the chloride ion in thepost-reaction solution in the presence of N0 and removing chlorine fromthe reaction product; oxidizing the nitrogen oxides in said gaseousmixture to additional nitric acid; neutralizing the unreacted nitricacid, in contact with the sodium nitrate, with ammonia in a mol ratio ofammonia to sodium nitrate of about 1:1; carbonizing the reaction mixturewith carbon dioxide to a yield of sodium bicarbonate ofabout 67 percentof theoretical as a precipitate;separating said sodium bicarbonate fromthe remaining solution of sodium nitrate and ammonium nitrate and alsoincluding ammonium bicarbonate and ammonium carbonate; and decarbonizingsaid ammonium bicarbonate and said ammonium carbonate and partiallyevaporating said solution at about 85 C to obtain a solution ofsodium-ammonium nitrate which is about percent ammonium nitrate and hasa total nitrogen content of about 30 percent.

2. The process as claimed in claim 1, wherein said sodium bicarbonate isprecipitated in large crystals.

3. The process as claimed in claim 2, wherein said sodium bicarbonate iscalcined to form sodium carbonate.

4. The process of claim 1 wherein said nitric acid which oxidizes sodiumchloride'is about 60 percent 70 percent concentrated and said nitricacid formed by oxidation of said nitrogen oxide is about 63 percent to98 percent concentrated.

5. The process of claim 1 wherein the mol ratio of nitric acid to sodiumchloride is about 2.24:1.

2. The process as claimed in claim 1, wherein said sodium bicarbonate isprecipitated in large crystals.
 3. The process as claimed in claim 2,wherein said sodium bicarbonate is calcined to form sodium carbonate. 4.The process of claim 1 wherein said nitric acid which oxidizes sodiumchloride is about 60 percent - 70 percent concentrated and said nitricacid formed by oxidation of said nitrogen oxide is about 63 percent to98 percent concentrated.
 5. The process of claim 1 wherein the mol ratioof nitric acid to sodium chloride is about 2.24:1.